1. Technical Field of the Invention
The present invention relates to a cutting tool.
2. Description of the Prior Art
The majority of existing cutting tools comprise an elongate handle and a blade portion having a cutting edge extending axially from the handle.
When using such a tool to perform a cutting operation, it is usual for a person to grip the handle of the tool and to draw the blade of the tool towards himself or sideways through a workpiece.
However, as the blade of the tool is released from the workpiece at the end of a cut, the person holding the tool often finds it difficult to maintain control of the tool, thus creating a serious safety hazard both to himself and to those around him.
An arrangement has been proposed wherein a tool is provided with a member which is biassed towards a safety position in which the member forms a guard for the blade of the tool, but which may be displaced to expose the blade by bringing the tool into cutting contact with a workpiece. The tool is further provided with a latch which must be released by depressing a trigger to allow the guard member to be displaced. Thus, inadvertent exposure of the blade is prevented.
However, in order to overcome the safety hazard described above, the trigger must be released before the end of a cut to allow the latch to re-engage the guard member as soon as the tool is released from a workpiece: we have found that there is a tendency for persons using such tools not to release the trigger in sufficient time to prevent accidental cuts from occurring.
We have now devised an arrangement which overcomes the above-mentioned limitations of existing cutting tools.
According to a first aspect of the present invention, there is provided a cutting tool having a blade and a member which is biassed towards a safety position in which the member forms a guard for the blade, but which may be displaced to expose the blade by bringing the tool into cutting contact with a workpiece, and a locking mechanism having a trigger which must be moved from a first position to a second position to release the guard member from its safety position and arranged such that each time the guard member is released from its safety position, is displaced through a predetermined distance, and then returns to its safety position, the guard member will become locked in place regardless of the position of the trigger.
Thus, as the blade of the tool is released from a workpiece at the end of a cut, the guard member is re-deployed and locked in place without the operator having to release the trigger.
Preferably the guard member is pivotally mounted to the tool.
Preferably the locking action of the cutting tool is provided by a strut which is pivotally joined to the guard member, the distal end of the strut being arranged to follow a loop. Most preferably the strut is arranged to pivot in a vertical plane.
Preferably a lug at the distal end of the strut slidably locates within a looped recess. Preferably the recess comprises a guide-channel which extends substantially perpendicularly to the axis of the longitudinal axis of the strut and within which the lug prevents substantial axial movement of the strut. Preferably as the trigger is displaced from said first position to said second position, the strut is displaced such that lug slides out of one end of the channel.
Preferably the locking mechanism is arranged such that the guard member cannot be released from said safety position unless the tool is in contact with the workpiece.
Preferably the blade is provided in a replaceable cartridge.
Cutting tools are also known in which a blade is mounted to a sliding blade-carriage for advancing and retracting the blade in predetermined increments. For example, it is known to form a blade with a number of lines of weakness defining successive blade sections which may be detached, one at a time, from the end of the blade to maintain a sharp edge to the blade. The blade-carriage may therefore be arranged to be advanced in increments equal to the width of each blade segment.
However, in many circumstances, it would be desirable for the blade to be advanced both in predetermined increments, for example as successive sections of the blade are detached, but also for the position of blade to be adjusted by a much finer degree, to control the depth of cut.
We have now devised an arrangement which provides both coarse and fine adjustment of the blade position.
According to a second aspect of the present invention, there is provided a cutting tool having a blade and a sliding blade-carriage formed with an elongate projection which extends substantially perpendicularly through a slot formed in the blade, the projection being rotatable about an axis parallel to its longitudinal axis and the slot being of substantially the same diameter as the projection and extending substantially perpendicularly to the axis of movement of the carriage, so that as the projection is rotated, the blade is correspondingly advanced or withdrawn relative to the carriage.
Thus the carriage may be slid to-and-fro to provide coarse adjustment of the blade position and the elongate projection may be rotated to provide fine adjustment of the blade position.
Preferably the blade is provided in a replaceable cartridge to which the blade-carrier is preferably mounted.
As mentioned above, it is known to provide a cutting tool with a blade formed with a number of lines of weakness defining successive blade sections.
However, in order to detach successive blade sections from the end of the blade it is typically necessary to press the end of the blade sideways against a hard surface to snap the blade along a line of weakness. The blade must therefore be exposed as the end section is detached and, should the cutting tool slip, injury may result. There is also the possibility that the detached blade portion may contaminate a product or cause injury as it is disposed of.
We have now devised an arrangement which overcomes these limitations of existing cutting tools.
According to a third aspect of the present invention, there is provided a cutting tool having a passageway for receiving a elongate blade formed with one or more lines of weakness defining successive blade sections, a portion of the tool being displaceable to detach a distal section of the blade from the remainder of the blade such that the detached blade section is retained within a containment region of the tool.
Preferably the displaceable portion comprises a portion of the passageway formed by opposed first and second walls pivotally mounted such that they may be displaced to one side of the passageway to allow an end section of the blade to be introduced into the gap thus formed, and then brought back into line with the passageway to detach the end section from the remainder of the blade.
Preferably the portion of the passageway formed by the first and second walls is arranged to pivot away from the passageway about the forward edge of the portion.
Preferably, the detached end section of the blade is pressed through an opening into the containment region.
Preferably the passageway is provided in a replaceable blade-cartridge, which may also provide the containment region for receiving detached blade sections.
Preferably the tool or, where the tool comprises a replaceable blade-cartridge, the blade-cartridge, is formed from a blank comprising three collinear elongate portions arranged to be folded together along their adjoining edges such that the passageway for receiving an elongate blade is formed between the opposed faces of two adjacent portions of the blank, and the containment region is formed between the opposed faces of one of the two adjacent portions and a face of the remaining portion.
Preferably the blank is arranged for two adjacent portions of the blank to be folded together, to form the passageway between their opposed faces, and for the portions on opposite sides of the blank to then be folded together, to form the containment region between their opposed faces.
Preferably the blank is formed from a plastics material having fold lines formed by compressed regions of the blank.
Preferably the opposed faces of the two portions which form the containment region are each formed with a plurality of projections for inhibiting movement of detached blade sections within the containment region.
It is known to provide a cutting tool with a replaceable cartridge from which a blade may be extended and retracted. However, such cartridges present a serious safety hazard where it is possible for the blade of the cartridge to be exposed when the cartridge is outside of the tool.
We have now devised an arrangement which overcomes this problem.
According to a fourth aspect of the present invention, there is provided a cutting tool comprising a replaceable blade-cartridge within which a blade is carried such that the blade may be slid from an exposed position to a retracted position and comprising means for preventing the cartridge from being removed from the tool whilst the blade is in its exposed position and means which lock the blade in its retracted position as the cartridge is removed from the tool.
Preferably the tool comprises a blade-carrier and the means for preventing the cartridge from being removed from the tool whilst the blade is in its exposed position comprises a pivoting catch having a first portion which engages a part of the tool body when the blade is in its exposed position, and a second portion which is displaced by the blade-carrier when the blade is in its retracted position to disengage the first portion from said part of the tool body.
Preferably the tool comprises a blade-carrier and the means which lock the blade in its retracted position as the cartridge is removed from the tool comprises a pivoting catch having a first portion which engages the blade-carrier when the blade is in its retracted position and the cartridge is outside of the tool, and a second portion which is displaced by a part of the tool body when the blade is inserted into the tool to disengage the first portion from the blade-carrier.
The arrangement thus significantly reduces the risk of the blade being exposed when the cartridge is outside of the tool.